Metal die-casting processes generally utilize a mold having a fixed insert presenting a first mold face which is pressed up against a movable insert presenting a second mold face. Molten metal, such as aluminum, is injected into a space between the fixed insert and the movable insert. The molten metal is allowed to solidify in the space and then the fixed and movable inserts are separated in a direction referred to herein as the "machine direction". The solidified metal (now a die-cast part) generally remains with the fixed insert and is removed or "stripped" from the fixed insert.
As long as the part only includes portions that taper away from the movable insert in the machine direction, forming and stripping are relatively straightforward. Occasionally, however, a part will include an opening which extends away from the movable insert in a direction not parallel to the machine direction and which must be surrounded by metal. If the part does not have a reduced diameter or breadth portion along the length of the opening, this can be accommodated by a "slide" that is pressed up against the core during forming and withdrawn prior to stripping of the part from the core.
Occasionally however, it is desirable to form such an opening which has a reduced breadth or diameter portion along its length with a larger diameter or breadth portion adjacent the movable insert. FIG. 1 is a sectional view of a prior art mold assembly for forming such a part.
FIG. 1 illustrates a typical movable insert at reference 10 and fixed insert 12 for molding a part 14 having an opening 16 which is narrower at reference 18 than it is adjacent the movable insert 10. To form the enlarged diameter portion adjacent the movable insert 10, an added (or "loose") core 20 is mounted over a shaft 22 extending from a slide 24. The mold, generally indicated by reference 26, is closed. Molten metal is injected into the space between the fixed insert 12, movable insert 10 and added core 24 to form the part 14. Once the molten metal has cooled, the slide is withdrawn and the movable insert 10 and fixed insert 12 are separated. The part, which will still contain the added core 20 is then stripped from the fixed insert and the added core 20 is pressed out.
Such a procedure is labour intensive and potentially dangerous, as an operator has to put their hand between the movable insert 10 and fixed insert 12 to place the added core 20 on the shaft 22. If the mold 26 were to inadvertently close, the operator's hand could get trapped and serious injury could result. Furthermore, if the added core 20 is not precisely mounted, defective parts may result.
It is an object of the present invention to provide a movable insert having a core which is movable between a retracted position in the movable insert to an extended position extending from the movable insert.
It is a further object of the present invention to provide such a core which is movable between the retracted and extended positions without manual intervention by a human operator.
It is a still further object of the present invention to provide means for preventing movement of the core toward the movable insert during molten metal injection.
It is another object of the present invention to provide a movable insert having a retractable core with means to lock the core in the retracted position.
It is yet another object of the present invention to provide a core locator releasably connectable to a retractable core for moving the core between its retracted and extended positions.